1. Technical Field
The present disclosure relates to a combined heat and power system.
2. Description of the Related Art
A combined heat and power system (CHP system) is a system configured to concurrently obtain multiple types of energy (such as heat and electric power) from a single resource or a plurality of resources. Recently, a CHP system that can be provided in a relatively small facility such as a hospital, school, or library or a CHP system (so-called micro CHP) for ordinary households is attracting attention in addition to a large CHP system.
In a CHP system, a Rankine cycle can be used as an electric power generation cycle. For example, European Patent Application Publication No. 2014880 proposes the use of a displacement type expansion machine for a Rankine cycle so as to meet a relatively small heat demand and electricity demand. In a CHP system for small facilities or ordinary households, fluctuations in heat demands such as the amount of heat consumption, the required temperature, and the like have large effects on the performance and efficiency of the CHP system.
The efficiency of a CHP system is represented by the ratio of the electricity and heat used efficiently to the fuel supplied to the CHP system. Efficient use of all electricity and heat obtained by a CHP system maximizes the total efficiency of a CHP system, thereby producing an advantage of installation of the CHP system. A CHP system that uses a Rankine cycle generates more heat than a CHP system that uses a gas engine. Effective use of heat improves the total efficiency of a CHP system.
In small facilities or ordinary households, the required amount of heat and the required temperature differ for each facility or household. In addition, even in a single facility or household, when, for example, heat is used for heating, fluctuations in the heating load and/or the required heating temperature are large between night and day. Fluctuations in the heating load and/or the required heating temperature are also large between winter and summer. Since a hot-water supply load is generated temporarily when heat is used for hot-water supply, fluctuations in the required amount of heat and the required temperature become large. Accordingly, small facilities or ordinary households require CHP systems that can meet the heat demand and the heat temperature that fluctuate significantly.